1. Field of the Invention
The present invention relates to a transmitting and receiving antenna for a portable radiotelephone with an antenna element which can be accommodated inside the case of the portable radiotelephone by being freely pushed into, and also withdrawn from, the case. More specifically, the present invention relates to a means of compensating for drops in reception sensitivity that occur when the antenna element is inside the case.
2. Prior Art
As is universally known, telephones are instruments which are used for two-way communication, and portable radiotelephones are also used in this way. In telephones for two-way communication it is absolutely impossible to predict when a call signal will be received from a calling party. Accordingly, in conventional portable radiotelephones, as shown in FIG. 6(a), the antenna element 1 is fixed so that it constantly projects outside of the case 2 of the portable radiotelephone, thus insuring that a call signal can always be received. Furthermore, the case 2 has the shape of a transmitter-receiver used in ordinary telephones.
Since the antenna element 1 constantly projects outside of case 2 in conventional antennas constructed as described above, antenna element 1 becomes a nuisance when the radiotelephones is not in use. Accordingly, it is desirable to accommodate the antenna element 1 inside the case 2 when the radiotelephone is not in use.
FIG. 6(b) illustrates a radiotelephone which is designed so that the antenna element 1 is simply accommodated inside the case 2 (so that it can be freely pushed into or withdrawn from the case). With such a construction, however, the transmission/reception sensitivity of the antenna element 1 drops conspicuously when the antenna element 1 is inside the case 2. As a result, the intrinsic function of the radiotelephone as a telephone, i. e., "the ability to receive call signals at all times," is reduced by half or more.